336 REPORT OF STATE BOARD OF HORTICULTURE. 



als, at least, survive protected in crevices or under bits of bark, and remain 

 more or less active during- winter and renew the colonies the following- 

 spring. This has been shown to be true in the Distx"ict of Columbia, and 

 also in the interior regions of the same latitude in spite of the much coldnr 

 winters. The root form survives the winter usually in an immature condi- 

 tion, namely, larva^ in various stages of development, and both in latitudes 

 where the aerial forms are killed by the severity of the winter and else- 

 where it seems probable that there is a regular upward migration in sprin;^ 

 and early summer from the roots, the aerial colonies appearing first near 

 the crown and at a later period on the higher parts of the trees. At any 

 time during the summer and fall there may be migrations to the roots, and 

 throughout the year the subterranean colonies are maintained. 



The spread of the insect is accomplished in part by the viviparous* 

 females, which appear in late summer, but quite as commonly perhaps by 

 the transporting- of young or partly grown individuals from tree to tree or 

 to distant orchards by means of birds or insects to which they have attached 

 themselves. Its wide distribution is usually dependent on the traffic in 

 nursery stock. 



REMEDIES AND PREVENTIVES. 



The foregoing account of the habits and characteristics of the woolly 

 aphis will enable us to suggest certain measures to control it. The aerial 

 form presents no especial difficulty, and can be very readily exterminated 

 by the use of any of the washes recommended for plant lice, such as kero- 

 sene emulsion, a strong soap wash, resin wash, etc., the only care nec- 

 essarj' being to see that the wash is put on with sufficient force and thor- 

 oughness to penetrate the covering and protecting cottony excretion. If 

 the wash be applied warm, its penetration will be considerably increased. 



The much more important root form, however, is more difficult to reach 

 and extermiuate. Any of the remedies which are applicable to the phyl- 

 loxera will apply to the apple root plant-louse, such as the use of bisulphide 

 of carbon or submersion. The common recommendations are of applications- 

 of strong soap or tobacco washes to the soil about the crown, or soot, ashes, 

 or tobacco dust buried about the roots ; also similarly employed are lim^^ 

 and gas lime. 



The most generally recommended measure hitherto is the use of hot 

 water, and this, while being both simple and inexpensive, is thoroughly 

 effective, as has been demonstrated by practical experience. Water at 

 nearly the boiling point may be applied about the base of young trees with- 

 out the slightest danger of injury to the trees, and should be used in suffi- 

 cient quantity to thoroughly wet the soil to a depth of several inches, as the 

 lice may peneti'ate nearly a foot below the surface. To facilitate the wet- 

 ting of the roots and the extermination of the lice, as much of the surface 

 soil as possible should be first removed. 



Some recent very successful experiments conducted by Mr. J. M. Stedmaii 

 have demonstrated the very satisfactory protective as well as remedial value 

 of finely ground tobacco dust. The desirability of excluding the aphis alto- 



